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Last updated 2010-08-09
|Searing is not sealing
Many cookbooks still recommend that a piece meat should be seared at high temperature to seal the juices. This is one of the most widespread kitchen myths and can be traced back historically to the German chemist, Justus von Liebig, who was convinced that high temperatures would coagulate surface proteins in the meat and thus seal of the surface to prevent further loss of juice from the meat. In his book "The Curious Cook", Harold McGee approaches the problem scientifically. He weighs slices of beef before and after cooking and what he finds is that meat that has been seared in fact loses more of the original weight than meat which is cooked at a lower temperature. The reason for this is that as the meat is heated, the proteins coagulate and squeeze water out of the muscle.
Despite this fact, it is still recommended to sear a piece of meat at high temperature. But this has to do with taste. When the temperature rises above 110-120 °C, proteins and amino acids start to react with sugars present. This reaction is known as the Maillard reaction, named after the French chemist Louis-Camille Maillard. The Maillard reaction produces characteristic brown and golden colors plus a large number of taste and aroma molecules. To understand the importance of the Maillard reaction, just think of the huge difference between meat cooked in boiling water and meat cooked in a skillet at a temperature above 120 °C. The Maillard reaction is not limited to the cooking of meat. We also find products of the Maillard reaction in potato chips, bread crust, fried onions - to mention just a few. Even in vintage champagne, one can find products of the Maillard reaction. Despite the fact that the champagne is not heated to above 120 °C, storing it for several years compensates for this. Put simply, at lower temperatures, the Maillard reaction simply takes much longer. For vintage champagne, the Maillard reaction can take several years to develop the characteristic compounds.
Low temperature cooking with DIY "sous vide"
One important aspect of molecular gastronomy is the application of scientific principles to food preparation in a normal kitchen. This can very well be illustrated by discussing the preparation of a steak. The surface of the meat needs to be heated to > 120 °C (250 F) for the Maillard reaction to take place at a reasonable rate. This gives meat much of it's characteristic aroma. The interior of the meat however should not be heated to more than 50-65 °C (120-150 F) for a rare or a medium rare appearance. If the heat is provided by a frying pan with a temperature typically in the range 120-160 °C (250-320 F), the different temperature required for the interior and the surface of the meat can actually be quite difficult to achieve. Bringing the meat to room temperature before cooking by taking it out of the fridge 1-2 hours in advance helps. Also, half way through the cooking it's advisable to let the meat rest on a plate to allow the heat to diffuse into the interior and to let the surface cool down a little.
There is however an easier way to make a perfect steak! In restaurants the method has been around since the 70's and is known under the name sous vide (fr. under vacuum). The meat is packed in plastic bags, vacuumed and put into thermostated water baths. This equipment is not (yet?) found in the average kitchen. So here is a simple DIY procedure. You just use a normal plastic bag, leave the meat in the water bath for 30 min (or longer) and then quickly fry both sides to generate the products of the Maillard reaction. You do need a thermometer though to control the temperature of the water bath, preferably one with a dip in probe.
1. Put the meat (I used a rib eye steak for this experiment) in a thick plastic bag. Only put one or two pieces of meat in each plastic bag - this ensures a greater contact surface with the water.
2. Add any spices you like (salt and pepper always works well - for the experiment shown I used curry paste, soy sauce and chili sauce in stead), press out the air and close the plastic bag tightly by tying a knot (or use a zip-lock bag). You don't want any water to enter the bag!
3. Heat a pot of water to the desired temperature (or use hot tap water) and place the plastic bag with meat in the water. Cover with a lid (not shown in the picture) to reduce heat loss. If you use a large pot of water it's easier to keep the temperature constant. Also, it's easier to control the temperature with an induction or gas stove top than with an electric plate since there is no additional heating once you turn them off. Regarding the temperature, start with 60 °C (140 F) and experiment from there (or check this table at Wikipedia for doneness temperatures of meat). You should leave the meat in the water for at least 30 minutes - more for a thicker cut. But the good thing is you can leave it for much longer (several hours) provided the temperature does not come above 60 °C (or whatever temperature you decided on). A convenient way to keep the temperature constant for a long time is to put the pan with water into the oven and use the thermostat of the oven.
4. Heat a frying pan, add a fat of you choice, remove meat from plastic bag and brown both sides of the meat. Since you take the meat directly from the water bath it's already at about 60 °C. Therefore the browning is very fast.
5. A temperature of 60 °C (140 F) gives the meat a pink interior. It's succulent and juicy. The short frying gives it a nice browned crust and the chewing resistance is perfect. All in all a wonderful combination of taste, aroma, texture and mouth feel!
Check out the book lists on molecular gastronomy and food chemistry.
More to come on marinades and brining!